﻿using System;

class Program
{
    static void Main()
    {
        float a = 9;
        float b = 9;
        float c = 9;

        float s = SideAndAltitude(a);
        Console.WriteLine(s);

        double s2 = ThreeSides(a, b, c);
        Console.WriteLine(s2);

        double s3 = TwoSidesAndAngle(a, c);
        Console.WriteLine(s3);


    }

    private static double TwoSidesAndAngle(float a, float c)
    {
        float beta = 60;
        double s3;
        s3 = (c * a * Math.Sin(beta)) / 2;
        return s3;
    }

    private static double ThreeSides(float a, float b, float c)
    {
        float p = (a + b + c) / 2;
        double s2;
        s2 = Math.Sqrt(p * (p - a) * (p - b) * (p - c));
        return s2;
    }

    private static float SideAndAltitude(float a)
    {
        float s;
        float h = 9;
        s = (a * h) / 2;
        return s;
    }
}